This proposal is for the purchase of a SkyScan 1172 micro computed tomography (CT) system, which will serve ten NIH-funded research groups. Our present micro CT system has been working at maximum capacity for five years, but its quality of image resolution is not adequate for applications to soft tissue or to any structures smaller than about 25 [unreadable]m. The demand for micro CT on our campus continues to grow, and the proposed system will allow excellent resolution of fine structure even in low contrast samples, so that new applications for micro CT can be accommodated or developed. The SkyScan 1172 can image specimens with very high resolution-less than 1 [unreadable]m voxel size and low-contrast resolution of 5 [unreadable]m. A typical scan takes only about one hour, and the system comes with a reconstruction workstation of clustered PC's and special software to allow rapid calculation of image slices, so that a user can reconstruct a scan while the next specimen is scanning. This will provide the high throughput required to service the needs of our research community for micro CT. Applications for the proposed facility include: 1) Elucidation of the fine structure of kidney stones, for studies of the mechanisms of stone breakage by shock wave lithotripsy and study of stone formation. 2) Visualization of fine structure of kidney biopsies taken from stone patients during surgery, showing the earliest stages of the formation of kidney stones. 3) Detection of the earliest stages of dental caries. 4) Mapping and quantitation of vascular calcification in chronic renal disease. 5) Quantitation and imaging of vascular beds in limbs and organs injected with contrast fill, to study peripheral vascular disease and myocardial infarction. 6) Imaging and quantitation of bone structure in studies of osteoporosis, of the genetic basis of bone architecture, of osteolytic cancer, drug effects on bone, development of microcracks, wound healing in bone, and of bone regrowth in artificial scaffolds. The acquisition of the SkyScan 1172 is essential for continued progress on these and future projects requiring this state-of-the-art technology. [unreadable] Relevance. This proposal is for purchase of a new micro CT ("cat" scanner) system, which will be used to study biological specimens from several laboratories. This technology will make possible new discoveries in the areas of bone disease (such as osteoporosis), blood vessel disease (including the deposition of calcium in vessels in chronic kidney disease), tooth decay, and kidney stone disease. [unreadable] [unreadable] [unreadable]